Physical objects, such as antennas must have provision for field installation. In particular, in a radio-based system, such as a G.P.S. (Global Positioning System) a radio portion is typically installed inside a vehicle. An antenna needs to be mounted on the exterior of the vehicle so it is able to receive signals from satellites. Since these G.P.S. systems are often installed in the field, rather than in a factory environment where assembly can be controlled precisely, the antenna mounting mechanism and method needs to be intolerant to improper installation. Typically, the antenna is installed through a hole in vehicle's trunk, or elsewhere through a sheet metal or fiberglass body panel. Since the operating environment of a vehicle can include wide temperature excursions, and high intensity shock and vibration, the antenna must be fastened securely to survive and remain attached to the mounting location.
A standard technique is to affix the antenna through the vehicle's body panel using a fastener. During installation the fastener is progressively tightened by applying a radial force. As the radial force is applied, the antenna and the fastener clamp around the body panel. To withstand the severe vehicular environment the fastener needs to be radially torqued to a prescribed torque rating. One common problem with this is that a special wrench with a torque indication must be used to ensure that the proper torque rating is applied.
As a practical matter many field installers of these G.P.S. antennas do not use a torque wrench and often tighten the fastener without regard to the actual force applied to the fastener. For that matter installers rarely reads installation instructions where recommendation on torque are stated. These situations rarely result in a properly torqued fastener, and often results in an over-torqued fastener because the installer wants to make sure the antenna is securely mounted. Since the antenna fasteners are typically threaded, quite often the threads are stripped, especially in the case of thermoplastic based fasteners and antennas. If stripped the antenna and fastener need to be replaced. This is not only costly but very inconvenient for the field installer. Moreover, if the fastener threads are partially fatigued due to excessive application of force the installer may not detect it, and the antenna-fastener assembly can fail later in the field. So field reliability is also a major concern.
On the other hand, if the fastener is not torqued enough, the antenna can fall off.
What is needed is an improved fastening system that is easy to install, and is reliable independent of the field installation abuse.